But it says this is only going to be matched by an even more dramatic increase in complexity.

It says there's a multiplicity of rules and regulations governing how climate change funding should be spent and this poses an enormous challenge to small Pacific island democracies.

An indication of how difficult it is to access this money is that, of the $US32 billion promised by the international community up until March this year, only $US2 billion has no far been dispersed.

In Nauru's case, the study found that there's been since 2005, 32 separate climate change projects, worth a total of $US19 million.

It says that Nauru's previous experience with trust funds, especially its phosphate trust funds, has made donors wary of contributing any money to a climate change trust fund.

However, the study suggests that Nauru would be best dealing with those donor countries that are prepared to put money into budget support so that it can determine its own priorities in the spending on climate change.